Methicillin-resistant Staphylococcus aureus (MRSA) is a highly antibiotic-resistant bacterium that affects the chronically and critically ill and is associated with higher hospital costs, increased hospital length of stay, and substantial risks for patient morbidity and mortality both during and after hospitalization. MRSA carriage can last from months to years, and studies have shown that both recent and long-term MRSA carriers remain at high risk for infection and can transmit MRSA to others. While MRSA is a well-characterized pathogen in hospitals, relatively little is known about MRSA in nursing homes despite the fact that some nursing home studies have found that residents may be 3 to 5 times as likely to carry MRSA as hospitalized patients. Furthermore, the residential and social activities associated with nursing homes may promote transmission and limit the practicality of hospital-based infection control guidelines such as patient isolation. This study will occur in the context of a countywide investigation measuring MRSA prevalence among residents in a large number of nursing homes. To date, this countywide study has found that MRSA prevalence varies substantially across nursing homes even after accounting for differences in MRSA importation. In this context, we will explore nursing home characteristics that are significantly associated with high overall MRSA prevalence. Identification of these characteristics may guide facility-level infection control policy and provide criteria for identifying facilities in need of MRSA assessment and intervention. We will further evaluate whether nursing homes with high MRSA prevalence have higher levels of environmental contamination with MRSA and poorer quality cleaning compared to those with low MRSA prevalence. Quality of cleaning will be assessed by placing a novel black light marker on objects of interest and checking for successful removal of this marker under UV light following routine cleaning. Finally, we will evaluate whether MRSA-positive patients have a lower acceptance rate into nursing homes compared to those who are MRSA-negative. This has implications for unintended consequences of legislation directing hospitals to routinely screen high risk patients for MRSA. Results of this study will fill critical gaps in our knowledge of MRSA prevalence, transmission, and prevention in nursing homes.